JP Norden, 22, and Paul Norden, 31, were outside the Forum Restaurant on Boylston Street with friends waiting for another friend to finish the race on April 15 when the second explosion went off. Both brothers lost a leg in the blast.

On Sunday the brothers hosted a fundraiser for their organization, the Norden Brothers Benefit Fund. Proceeds from the event will help the siblings pay medical bills and fund other long-term care needs.

"They came here to watch a good friend run the marathon and now they're in a marathon for their lives," said their uncle Peter Brown.

The brothers were also at the finish line area a couple of months ago to meet family members who walked the Hopkinton to Boston route to raise funds.

"It’s about getting the boys back to finish what they started that day," their mother, Liz Norden said. "For me it just doesn't end so to have them back here where their lives changed is a big thing."